Ignition system



March l, 1949. a. H, SHORT ETA. *2,463,123

IGNITION SYSTEM Filed Aug. 18. 1945 ArroRNEY/f Patented Mn. 1, 1949- IGNITION SYSTEM Brooks n. slm-i, anderson, .ma Andrew` o. Tynan, Kokomo, Ind., assignors to General Motors Corporation, Detroit. Michga corporation of Delaware Application Allnet 18, 1945, Serial No. 611,402 k This invention relates to an ignition system for an internal combustion engine and more particularly for automotive use. i

It isan object or the present invention to provide an ignition system of high frequency such as will provide satisfactory ignition for an engine operating under a relatively high compression even when the spark plugs are fouled. In the disclosed embodiment of the present invention, thisobject is accomplished by the use of a direct current source for charging a main condenser and an auxiliary condenser and bycontrolling the discharge of the main condenser through the primary circuit of a high frequency ignition coil by means of a hydrogen nlled thyratron which is caused to be conductive by the discharge of the auxiliary condenser, the discharge of which is effected by the closing of the timer contacts.

A further object of the invention is to provide a suitable high frequency ignition coil.

Further objects and advantagesof the present invention will be apparent from the following description, reference being had to the accompanying drawing, wherein a preferred embodiment of the present invention is clearly shown. In the drawings:

Fig. 1 is a wiring diagram illustrating a form of the invention. l

Fig. 1A is a chart illustrating the operation. e Fig. 2 is a plan view of the .ignition coil together with its housing and terminals, the cover of the housing being removed.

Fig. 3 is a sectional view on except that the ignition coil vation.

Fig. 4 is a plan view of one of the ignition coil sections.

Fig. 5 is a plan View of the ignition coll core.

Fig. 6 is a fragmentary, sectional view of one of the ignition coil sections showing the primary and secondary winding layers and layers of insulation.

Referring to Fig. 1, a terminal 'i0 is connected line 3 3 of Fig. 2, is shown in side elewith a high voltage D. C. source for example. one

which will impress a voltage of 2500 volts between terminal iii and ground y. Voltage divider resistances ii and i2 are connected between terminal iii and ground. Between the tap i3 and ground, there is a voltage drop of 200 volts. A resistance i4 connects tap i 3 with an auxiliary condenser I5 which is charged, for example, at 200 volts. Terminal i is connected by resistance I6 with the main condenser i1 connected with primary P of an ignition coilk 30 whose secondary S is connected with an ignition distributor 20 by which connections are made in recurrent sequence with the various spark plugs 2| of the engine.

The discharge of condenser Il vis controlled by a hydrogen lled thyratron 22 having a plate 23 2 Claims. (Cl. 12S-148) 2 connected with condenser I1, having a grid 24 connected through resistance 2l with a contact 28 of anignition timer engageable with a timer contact 2l connected with condenser i5. The cathode 28 is connected between ground and terminal 28a on which is impressed a voltage of, for example, six volts for heating the cathode. A resistance 29 is connected between the cathode and the grid in order to prevent the tube 22 becoming conducting except at the proper time.

The operation of the system is as follows: Before the timer contacts 26 and 21 are closed, the condenser il has been charged .by the current source thru a circuit which includes terminal I0, resistance i6, condenser il, primary P of coil 30, and ground return to the current source. Also the condenser i5 has been charged by the current source through the circuit which includes terminal i0, resistance Ii, tap I3. resistance It, condenser i5 and ground return. While the contacts are open, the tube 22 passes no current. At the yinstant ignition is required timer contacts 26 and 21 close thereby causing condenser I5 to discharge through a circuit which includes a condenser i5, contacts 21, 26, resistance 25, grid 2,cathode 28 and ground return to the condenser. The discharge of condenser l5 causes the tube 22 to become conducting whereupon the condenser i1 discharges through a circuit which includes cathode 28, plate 23, condenser il, primary P of coil 3Q and ground return to cathode 23. Coil 3i) is so constructed that a current of high voltage and frequency is generated in the secondary S suilcient for ignition purposes even under conditions when the engine compression is high and spark plugs are fouled. It is only during the time condensers i5 and Ii are discharging through tube 22, that tube 22 is drawing current from the power supply through the resistance it, although contacts 26 and 21 may remain closed thereafter. In this way the energy of the power supply is conserved.

A satisfactory high frequency ignition coil for use with the system will now be described with reference to Figs. 2 through 6. Primary P of coil 30 comprises two sections 3| each having four coils 32 in parallel. Secondary S has two sections 35 connected in series. There are two ignition coil units C y(Fig. 4) each comprising four primary coils 32 and one of the secondary coil sections 35 wound upon the primary coil. An enlarged, sectional view of the unit C is shown in Fig. 6. To wind the coil unit. layers of insulating paper 40 are wound upon a removable core and four primary wires are grouped together and wound simultaneously in two layers with layers of insulating paper 4I between the layers of windings. 'I'hls will locate the start leads 33 and the end leads 34 of the primary coils 32 on the same end of the coil unit C as shown in Fig. 4.

Upon the second layer of primary coils 32 a number of Alayers of insulating paper 42 are wound. The turns of a secondary coil 35 are wound over the insulating paper 42 beginning at the end of the assembly o'pposite to that from which the leads of the primary extend. The secondary coill 35 is wound in two layers so that the leads 33 and 31 of the secondary 35 extend from the same end of the coil unit C, that end being opposite the end from which the primary leads 33 and 34 extend. There is a layer of insulation 43 between the ytwo layers of secondary turns and a wrapping of insulation 44 on the outside.

The two sections C surround parts of the core 45 which is formed by wrapping a thin steel strip upon a form to produce the shape shown in Fig. 5. A preferred material for the winding strip is hypersil steel .022 inch thick. After winding, the core -is severed at the lines :e and y to provide two parts which are butted together after the coil sections C are assembled with the core, and are retained by a band 48 which is wrapped around the core and the ends joined as indicated at 41.

The core and coil assembly is housed in a box 50 having a mounting bracket 5I. The assembly is retained by angle brackets 52 secured to the box 50. As shown in Flg.2, the coil sections C are positioned on the core 45 so that the primary leads are adjacent one side of the box 50 and the secondary leads are adjacent the opposite side of the box. Box 50 supports insulators 55a and 55h which support a terminal screw 54 retained by a nut 54a. To screw 54, the nongrounded lead 53 of the secondary coils 35 is connected. Wire 55 connects the two secondary coils. The other end lead 51 of the secondaries is .grounded on the box 50. Terminal screw 54 is connected, as indicated in Fig. 1, with distributor 20.

The start leads 33 of one primary section 3i. are attached to the finish leads 34 of the `other primary section 3l and to exible cables, and vice versa. The grounded flexible cable 58 is attached to the box 50. The non-grounded ilexible cable 59 is connected with a terminal screw 50 passing through insulators 5Ia and SIb supported by the can 50 and held in assembled relation by a nut 60a. Terminal 50 is connected with condenser I1 as shown in Fig. 1.

All of the primary windings 32 operate cumu-, latively and the secondary windings also operate cumulatively. The parallel connections of the primary provide a path of relatively low resistance for the discharge of current from the condenser II and the secondary sections 45 being connected in series increase the output voltage over that obtained from one coil, the resultant increased voltage being available for ignition purposes.

Satisfactory electrical dimensions are as fol lows:

Resistance I I, megohms, 2 watts Resistance I2, .5 megohm, 1 watt Resistance I4, .8 megohm, 1 watt Resistance I 6, 100,000 ohms, 50 watts Resistance 25, 2,500 ohms Resistance 29, 25,000 ohms Condenser I5, .001 micro-farad Condenser I1, .02 micro-farad Each coil 32, 11 turns of #28 varnish-insulated wire Each coil 35, 62 turns wire The thyratron tube 22 should contain hydrogen of #28 varnish-insulated or similar gas because its operation is not appreciably affected by temperature variations in the rang'eordinarily encountered in ignition service.

Referring to Fig. 1A, vertical line D-A represents the instant of closing of contacts 25, 21 and vertical line F-C the instant of contact opening. During time AB, condenser I5 discharges to render tube 22 conducting and the condenser I1 discharges and ignition is eiected. At B, tube 22 ceases to conduct because the condenser IT has discharged and the voltage of condenser I5 is very low because the-voltage available at I3 has been reduced by resistance I4 to avery low value at condenser I5. It will be seen that. while contacts 25, 21 are closed, there is a voltage divider circuit which includes resistances I4, 25, and 29 in series. Since resistance I4 has much greater resistance value than resistances25 and 29 .and condenser u I5'is connected between resistances I4 and 25, the voltage which the condenser I5 receives while the contacts are closed is a very low value represented by line G-H. When contacts 25, 21 open, the chargingl of condenser i5 begins and its voltage 4rises as represented by curve HI. The resistance value of resistances I4, should not be too high else the condenser I5 would not be charged in the time allowed and should not be too low else the voltage on condenser I5 would be so high that tube 22 would remain ionized during' the period A-C when the contacts are closed and the tube 22 would be drawing current from the power supply and energy would be wasted. One aim is to minimize consumption of energy which is represented by the shaded area in Fig. 1A bounded by lines A-B and D-'E which represent the time during which the tube 24 is ionized and lines D-A ang E-B which represent current passed by the tu e.

v"The function of resistance I4 is to control the rate of charging of condenser I5. It holds the voltage applied to condenser I5 to a very low value until the contacts open and permits the voltage of the condenser to increase, in the time allowed, to a value suiicient to eect ionization of tube 22 when the contacts close.

II'he function of resistance 25 is to limit the current passing to the grid of tube 24 during the ionization period.

The function of resistance 29 is to prevent the grid 24 from floating thereby preventing the tube 22 from becoming conducting except at the proper time.

The function of resistance I 5 is to limit the charging current of condenser I1. At the instant represented by line E-B when the tube 22 ceases to conduct, the charging of condenser I1 begins. As the condenser I1 receives charge, its charging current is represented by line EJ. If resistance I5 were omitted and terminal I0 were directly connected with the condenserA I1 and the plate 23 of tube 22, the charging of condenser I1 would begin at a very high rate under high potential and the tube 22 would be destroyed. The resistance I6 holds back the charging peak current by effecting a substantial voltage reduction so that charging begins at a moderate current value represented by line E-B.

While the embodiment of the present invention as herein disclosed, constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

Y What is claimed is as follows:

1. An ignition system comprising a direct cur- 75 rent source, a high frequency ignition coil having primary and secondary windings, a distributor connected with the secondary coils, a main condenser, a main condenser charging circuit including the source, the main condenser and a resistance for limiting the charging circuit to a suitable maximum, a main condenser discharging circuit including the main condenser, the primary windings voi the ignition coil and a thyratron, an auxiliary condenser, an auxiliary condenser charging circuit including the source, a resistance and the auxiliary condenser, and an auxiliary`- condenser discharging circuit including the auxiliary condenser, the contacts of an ignition timer and the grid of the thyratron, ithe closing of the timer contacts causing the auxiliary condenser to discharge to the thyratron grid tap of the voltage divider, an ignition timer having contacts one of which is connected to a terminal of the auxiliary condenser, a fourth resistance connected to the other timer contact and the grid of the thyratron for controlling the discharge of the auxiliary condenser to the grid and render the thyratron conducting whereby the.

main condenser discharges and ignition is provided, the value ofthe second mentioned resistance being such that, after the auxiliary condenser has discharged, the thyratron ceases to conduct because the voltage at the auxiliary condenser is held by the said resistance to a low value while the timer contacts are closed.

2. An ignition system comprising a direct current source, a high frequency ignition coil having primary and secondarywindings, a distributor connected with the secondary coils, a main condenser, a main condenser charging circuit including the source, the main condenser and a resistance for limiting the charging current` to a suitable maximum, a main condenser discharging circult including the main condenser, the primary windings of the ignition coil and a thyratron, an auxiliary condenser, a voltage divider resistance connected with the current source, an auxiliary condenser charging circuit including the auxiliary condenser and a third resistance connected to a" values of the fourth and fifth resistances whereby` the voltage at the auxiliary condenser is held to such low value after the auxiliary condenser has discharged and before the contacts open that the thyratron ceases to conduct after the auxiliary condenser has discharged.

BROOKS H. SHORT. ANDREW G. TYNAN.

narnnancns CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,175,900 Knight 4---- Oct. 10, 1939 2,203,579 Randolph f June 4, 1940 2,278,481 Peters et al. Apr. 7, 1942 2,378,791

Robinson et al. June 19, 1945 

